Founded in 1993 by brothers Tom and David Gardner, The Motley Fool helps millions of people attain financial freedom through our website, podcasts, books, newspaper column, radio show, and premium investing services.

Just because this chain isn't the biggest doesn't mean it's not the best.

Despite the tens of millions of customers that buy Starbucks coffee every year, it still wasn't the highest-rated coffee shop when it comes to how satisfied they are with their cup of joe.

The complaints consumers most often give for why they refuse to drink Starbucks(NASDAQ:SBUX) coffee include the burnt taste of its coffee and its higher than average prices.

Although the reputation for selling overpriced coffee isn't completely fair (depending on where you buy it, a small coffee is around $1.75, a not outlandish sum even in relation to its rivals), sometimes it's hard to live down a bad rap, and Starbucks' recent decision to raise prices on many of its hot beverages doesn't help its image.

Still, the coffeehouse has tried to meet some of the criticisms, such as the "blonde roast" it introduced a few years ago to please those of us who prefer a milder taste.

But apparently that isn't enough, because when the American Customer Satisfaction Index released its restaurant report for 2015, detailing how satisfied consumers were with different chains, Starbucks came in 11th place out of 18 limited-service restaurants, with its rating sliding 3% to 74. That also put it in second place for coffee shops.

What have you done for me lately?The analysts offered up a few explanations for Starbucks' setback, noting that even though it brought premium coffee to the mainstream, it's being challenged by independent coffee shops and high-end coffee roasters, as well as by non-traditional outlets such as McDonald's(NYSE:MCD), which has become almost as well known for its coffee as it is for its burgers.

Starbucks has responded to those challenges both by going incognito with stealth shops and by opening more adult-oriented stores, including Starbucks Evenings and its new Reserve Roastery & Tasting Room.

But McDonald's has deeper problems, and it also fared poorly in the customer-service rankings, actually coming in dead last on the list. The burger chain has only been able to record flat or positive comparable sales growth for the past few years during months when it was offering its coffee for free.

McDonald's coffee remains one of the hamburger stand's strongest selling points, but it's not enough to overcome the other problems the chain has.

It's not me, it's youYet virtually the entire limited-service restaurant industry is finding it difficult to please the increasingly exacting demands of consumers.

ACSI found the overall ratings of these chains dropped almost 4% this year to 77 -- putting Starbucks just below average -- and that compared to full-service chains, the gap between them widened to its largest spread in five years.

When viewing all of the benchmarks ACSI used to rank the chains, fast-food restaurants suffered a collapse in customer satisfaction, accuracy of orders, quality of food and drinks, and staff courtesy.

Wake up and smell the coffeeBut not everyone rated poorly. In fact, the consumers' top choice for best coffee shop in the 2015 ACSI report was also the only one to record a higher score year to year.

Dunkin Brands' (NASDAQ:DNKN) Dunkin' Donuts restaurant saw its customer-satisfaction rating jump to 78, a 4% increase from the 75 rating it garnered a year ago.

ACSI believes the rollout last year of a new national member rewards program that was tied to its mobile app allowed it to score big points with consumers, even if more accolades are awarded to Starbucks' member program and mobile solutions.

Dunkin' Donuts was the only fast-food chain to score higher customer-satisfaction ratings this year compared to last year.

Perhaps because the doughnut shop is more of a fast-food restaurant than is Starbucks, and loyalty rewards programs aren't as common in the space, customers receive it more enthusiastically.

But CNBC believes it could be because you can get a free cup of coffee faster at Dunkin' Donuts as you can at Starbucks. CNBC found it takes just nine visits at the doughnut shop to get a free cup of coffee in the loyalty program, compared with 12 at Starbucks.

To be fair, CNBC also found that Dunkin' Donuts required you to spend almost $5 each visit to get the free coffee that quickly, while there was no dollar minimum at Starbucks. Further, if you buy just a coffee at the doughnut shop you need to make almost two dozen trips to get the free drink.

America really does run on Dunkin' DonutsStill, the membership rewards program coincided with the doughnut shop's major expansion plans, and making its coffee available to more people has apparently worked. In 2014, Dunkin' Donuts added 704 net new restaurants globally, including 405 in the U.S., helping to push revenues up almost 5% year over year. Comps, though, only increased incrementally, rising 1.6% (in comparison, Starbucks opened 1,600 stores worldwide and enjoyed a 6% jump in comps).

Customer satisfaction is a very subjective topic. And while Starbucks has its detractors, it has many more millions who are devoted to the brand. Dunkin' Donuts is trying to accelerate growth nationally, and at half the size of Starbucks in terms of number of stores in operation worldwide, there is plenty of room to grow. Starbucks has more than 22,000 stores worldwide to 11,300 Dunkin' Donuts shops, though it has over 7,500 Baskin-Robbins stores, too.

But if it's able to continue satisfying customers as it's been, Dunkin' Brands may yet become the premier coffee shop in sales, too.

Author

Rich has been a Fool since 1998 and writing for the site since 2004. After 20 years of patrolling the mean streets of suburbia, he hung up his badge and gun to take up a pen full time.

Having made the streets safe for Truth, Justice and Krispy Kreme donuts, he now patrols the markets looking for companies he can lock up as long-term holdings in a portfolio. So follow him on Facebook and Twitter for the most important industry news in retail and consumer products and other great stories.